Keystone eliminator for portable projection screens



P 1965 J. A. GUSKE 3,205,772

KEYSTONE ELIMINATOR FOR PORTABLE PROJECTION SCREENS Filed NOV. 16, 1961 in the images projected upon the screen.

United States Patent 3,205,772 KEYSTONE ELIMINATOR FOR PORTABLE PROJECTION SCREENS James A. Guske, Morton Grove, IlL, assignor to Radiant Manufacturing Corporation, Morton Grove, 111., a corporation of Illinois Filed Nov. 16, 1961, Ser. No. 152,774 Claims. (Cl. 88-28.91)

Conventional portable projection screens usually include an upright tubular supporting member provided with collapsible legs, a screen case pivotally and adjustably carried by the tubular supporting member, a roller mounted flexible screen carried by the screen case and provided with a bail for withdrawing the screen from the screen case, an extension rod telescopically carried by the tubular supporting member and adjustably projecting thereabove, and a hook member on the extension rod for receiving the bail to support the screen in vertical picture exhibiting position for projection of images thereon" by a projector.

When the vertical screen of such a conventional portable projetcion screen is situated considerably above the projector, as where projected images are being displayed to large audiences, the images projected on the vertical screen become distorted, this distortion being known as a keystone effect. To eliminate this keystone effect, it is necessary to tilt the screen forwardly so that the plane of the screen is substantially normal to the axis of the light projected by the projector onto the screen.

The principal object of this invention is to provide a keystone eliminator for a conventional portable projection screen in the form of an elongated bracket, which may be readily removably mounted at desired positions on the extension rod so as to receive the bail and support the screen in desired tilted positions for non-keystoning projection purposes, and which may be readily removably mounted on the tubular supporting member in parallel relation thereto for storage and transportation purposes with minimum space requirements.

Briefly, in accordance with this invention, the elongated bracket is provided with a plurality of spaced apart notches along one of the longitudinal edges thereof for selectively receiving the bail of the screen, and one end of the bracket is provided with means for removably mounting the elongated bracket at desired positions on Y the extension rod with the elongated bracket extending laterally above and beyond the screen case and with the notches in said longitudinal edge facing upwardly. As

upwardly facing notches to eliminate keystoning eifects Preferably, the removable mounting means comprises a pair of spaced apart ears extending from the end of the elongated bracket which are provided with oppositely directed aligned flanges for encompassing the extension rod at spaced apart points therealong, the ears and their flanges gripping the -extension rod, by reason of the torque on the elongated bracket, for removably mounting the bracket at desired space requirements. Preferably, in this respect, one end of the elongated bracket is provided with a magnet for engaging the tubular supporting member and the other end of the elongated bracket is provided with a ring to he slipped over the extension rod and/or a keyhole slot to "ice receive a screw which secures a cap on the upper end of the tubular supporting member.

Further objects of this invention reside in the details of construtcion of the keystone eliminator, in the cooperative relationships between the component parts thereof, and in the cooperative relationships between the keystone eliminator and the portable projection screen.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawing in which:

FIG. 1 is a view illustrating a conventional portable projection screen with the keystone eliminator of this invention applied thereto and with an image being projected upon the screen by a projector.

FIG. 2 is an enlarged perspective view of the upper portion of FIG. 1 illustrating the keystone eliminator mounted on the extension rod of the conventional portable projection screen.

FIG. 3 is a perspective view of a portion of the keystone eliminator illustrated in FIGS. 1 and 2.

FIG. 4 is an exploded perspective view illustrating the keystone eliminator as it is about to be removably secured to the tubular supporting member of the portable projection screen.

FIG. 5 is a view similar to FIG. 4 but illustrating the keystone eliminator removably mounted on the tubular supporting member of the portable projection screen.

Referring first to FIG. 1, a conventional portable projection screen is generally designated at 10. It includes an upright tubular supporting member 11 which is provided with collapsible legs 12, the legs 12 being extended as illustrated in FIG. 1 for supporting the projection screen and being collapsed against the tubular supporting member 11 for storage and transportation purposes. A handle member 13 is adjustably positioned on the tubular supporting member 11 and it pivotally carries a screen case 14, the screen case 14 being swung to a horizontal position, as illustrated in FIG. 1, for picture projection purposes, and being swung to a vertical position parallel to the tubular supporting member 11 for storage and transportation purposes. A roller mounted flexible screen 15 is carried by the screen case 14 and it is provided with a suspension slat 16 and a bail 17 for withdrawing the screen from the screen case 14 for picture projection pur- I poses.

The upper end of the tubular supporting member 11 is provided with a cap 18 which is secured in place thereon by a headed screw 19. An extension rod 20 extends through the cap 18 and is telescopically carried by the tubular supporting member 11. The extension rod 20 projects above the tubular supporting member 11 and it is adjustably secured in desired positions by means of a nipping lever 21 carried by the tubular supporting member 11 below the cap 18. The upper end of the extension rod 20 is provided with a hook member 22 having a slot 23 for receiving the bail 17 of the screen 15 for supporting the screen 15 in vertical picture exhibiting position for projection of images thereon by a projector 24.

In the normal use of such a conventional projection screen, the projector 24 is ordinarily at about the same level as the vertical screen 15 so that the axis 25 of projected light is ordinarily normal to the plane of the vertical screen 15. However, when the vertical screen 15 is situated considerably above the projector 24, as where projected images are being displayed to large audiences, the images projected on the vertical screen become distorted, this distortion being known as a keystone effect. As expressed above, to eliminate this keystone effect it is necessary to tilt the screen 15 forwardly so that the plane of the screen 15 is substantially normal to the axis 25 of 3 the light projected from the projector 24 onto the screen, he tilted position of the screen 15 being so illustrated in In order to support the screen 15 of the conventional portable projection screen in the forwardly tilted position, as illustrated in FIG. 1, the keystone eliminator of this invention is utilized. The keystone eliminator comprises an elongated bracket 30 which, for example, may be some 16 inches or so long. One of the longitudinal edges of the bracket 30, the upper edge as illustrated in FIGS. 1 and 2, is provided with a plurality of spaced apart notches 31 for selectively receiving the bail 17 of the screen 15, the particular notch selected determining the forward tilting of the screen 15. One end of the elongated bracket 30 is provided with a pair of spaced apart ears 32 and 33 which in turn are provided with oppositely directed aligned flanges 34 and 35, respectively. These ears and flanges encompass the extension rod 20 at spaced apart points therealong, the ears and their flanges gripping the extension rod, by reason of the torque exerted on the elongated bracket 30, for removably mounting the bracket 30 at desired places on the extension rod 20 without the need for extraneous fastening devices. Thus, when the elongated bracket 30 is so removably hung or supported on the extension rod 20, as illustrated in FIGS. 1 and 2, the bail 17 of the withdrawn screen may be received in a desired notch 31 in the upper edge of the elongated bracket 30 for providing the desired forward tilt to the screen 15 so that it will be normal to the axis 25 of the projected light from the projector 24 and thus eliminate the keystone effect. The weight of the screen 15 on the elongated bracket 30 operates through a torque action to firmly secure the elongated bracket 30 to the extension rod in any desired position.

When it is desired to store or transport the portable projection screen 10, the elongated bracket 30 is removed from the extension rod 20 so as to provide minimum space requirements for the assembly. When this is done, the elongated bracket 30 is removably secured to the tubular supporting member 11 in parallel relation thereto, as illustrated in FIGS. 4 and 5, so that there is no elongated bracket extending laterally from the collapsed portable projection screen.

Towards this end, a magnet 37 is secured to one end of the elongated bracket 30 by a rivet 38 extending through a suitable hole in the bracket. This magnet 37 engages the side of the tubular supporting member 11 so as to secure this end of the elongated bracket 30 thereto. The other end of the elongated bracket 30 is provided with a keyhole slot 39 which receives the headed securing screw 19 for the cap 18, the screw 19 and the keyhole slot 39 removably securing this other end of the elongated bracket 32 to the tubular supporting member 11. This latter end of the elongated bracket 30, as for example the ear 32 on this end of the bracket, is also provided with a hole 40 for receiving a ring 41 (FIG. 3) which may be slid over the extension rod 20 for securing this end of the elongated bracket 30 to the tubular supporting member 11. The ring 41 may be utilized in connection with those portable projection screens which do not have a headed securing screw 19 for the cap 18. Thus, it is seen that for storage and transportation purposes the elongated bracket 30 is readily secured to the tubular supporting member 11 at two spaced apart points in parallel relation thereto.

While for purposes of illustration one form of this invention has been disclosed, other forms thereof may be come apparent to those skilled in the art upon reference to this disclosure and, therefore, this invention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. A keystone eliminator for a portable projection screen having a tubular supporting member, a screen case carried by the tubular supporting member, a roller mounted flexible screen carried by the screen case and provided with a bail for withdrawing the screen from the screen case, and an extension rod telescopically carried by the tubular supporting member and adjustably projecting thereabove, comprising in combination, an elongated bracket having a plurality of spaced apart notches along one of the longitudinal edges thereof for selectively receiving the hail of the screen, and a pair of spaced apart ears extending from one end of the elongated bracket and provided with oppositely directed aligned flanges for encompassing the extension rod at spaced apart points therealong to removably mount the elongated bracket at desired positions on the extension rod with the elongated bracket extending laterally above and beyond the screen case and with the notches in said longitudinal edge facing upwardly, whereby the withdrawn screen may be tilted to desired degrees by placing the bail thereof in the appropriate upwardly facing notches in the bracket to eliminate keystoning effects in images projected upon the screen.

2. A keystone eliminator for a portable projection screen having a tubular supporting member, a screen case carried by the tubular supporting member, a roller mounted flexible screen carried by the screen case and provided with a bail for withdrawing the screen from the screen case, and an extension rod telescopically carried by the tubular supporting member and adjustably projecting thereabove, comprising in combination, an elongated bracket having a plurality of spaced apart notches along one of the longitudinal edges thereof for selectively receiving the hail of the screen, and a pair of spaced apart ears extending from one end of the elongated bracket and provided with oppositely directed aligned flanges for encompassing the extension rod at spaced apart points therealong to removably mount the elongated bracket at desired positions on the extension rod with the elongated bracket extending laterally above and beyond the screen case and with the notches in said longitudinal edge facing upwardly, whereby the Withdrawn screen may be tilted to desired degrees by placing the bail thereof in the appropriate upwardly facing notches in the bracket to eliminate keystoning effects in images projected upon the screen, and means on the elongated bracket for removably securing the same to the tubular supporting member in parallel relation thereto.

3. A keystone eliminator for a portable projection screen having a tubular supporting member, a screen case carried by the tubular supporting member, a roller mounted flexible screen carried by the screen case and provided with a bail for withdrawing the screen from the screen case, and an extension rod telescopically carried by the tubular supporting member and adjustably projecting thereabove, comprising in combination, an elongated bracket having a plurality of spaced apart notches along one of the longitudinal edges thereof for selectively receiving the hail of the screen, and a pair of spaced apart ears extending from one end of the elongated bracket and provided with oppositely directed aligned flanges for encompassing the extension rod at spaced apart points therealong to removably mount the elongated bracket at desired positions on the extension rod with the elongated bracket extending laterally above and beyond the screen case and with the notches in said longitudinal edge facing upwardly, whereby the withdrawn screen may be tilted to desired degrees by placing the bail thereof in the appropriate upwardly facing notches in the bracket to eliminate keystoning effects in images projected upon the screen, and means adjacent each end of the elongated bracket for removably securing the same to the tubular supporting member in parallel relation thereto.

4. A keystone eliminator for a portable projection screen having a tubular supporting member, a screen case carried by the tubular supporting member, a roller mounted flexible screen carried by the screen case and provided with a bail for withdrawing the screen from the screen case, and an extension rod telescopically carried by the tubular supporting member and adjustably projecting thereabove, comprising in combination, an elongated bracket having a plurality of spaced apart notches along one of the longitudinal edges thereof for selectively receiving the bail of the screen, and means on the elongated bracket for removably mounting the same at desired positions on the extension rod with the elongated bracket extending laterally above and beyond the screen case and with the notches in said longitudinal edge facing upwardly, whereby the withdrawn screen may be tilted to desired degrees by placing the bail thereof in the appropriate upwardly facing notches in the bracket to eliminate keystoning elfects in images projected upon the screen, and means including a ring adjacent one end of the elongated bracket to be slipped over the extension rod and a magnet adjacent the other end of the elongated bracket to engage the tubular supporting member for removably securing the elongated bracket to the tubular supporting member in parallel relation thereto.

5. A keystone eliminator for a portable projection screen having a tubular supporting member, a screen case carried by the tubular supporting member, a roller mounted flexible screen carried by the screen case and provided with a bail for withdrawing the screen from the screen case, a cap on the upper end of the tubular supporting member, a screw securing the cap in place, and an extension rod extending through the cap and telescopically carried by the tubular supporting member and adjustably projecting thereabove, comprising in combination, an elongated bracket having a plurality of spaced apart notches along one of the longitudinal edges thereof for selectively receiving the bail of the screen, and means on the elongated bracket for removably mounting the same at desired positions on the extension rod with the elongated bracket extending laterally above and beyond the screen case and with the notches in said longitudinal edge facing upwardly, whereby the withdrawn screen may be tilted to desired degrees by placing the bail thereof in the appropriate upwardly facing notches in the bracket to eliminate keystoning effects in images projected upon the screen, and means including a keyhole slot adjacent one end of the elongated bracket to receive the securing screw for the cap and a magnet adjacent the other end of the elongated bracket to engage the tubular supporting member for removably securing the elongated bracket to the tubular supporting member in parallel relation thereto.

References Cited by the Examiner UNITED STATES PATENTS 1,034,365 7/ 12 Hauser 248246 2,931,101 4/60 Martin 33-50 3,022,816 2/ 62 Petrick et al -24 FOREIGN PATENTS 729,3 62 5/55 Great Britain.

JULIA E. COINER, Primary Examiner.

NORTON ANSHER, Examiner. 

1. A KEYSTONE ELIMINATOR FOR A PORTABLE PROJECTION SCREEN HAVING A TUBULAR SUPPORTING MEMBER, A SCREEN CASE CARRIED BY THE TUBULAR SUPPORTING MEMBER, A ROLLER MOUNTED FLEXIBLE SCREEN CARRIED BY THE SCREEN CASE AND PROVIDED WITH A BAIR FOR WITHDRAWING THE SCREEN FROMTHE SCREEN CASE, AND AN EXTENSION ROD TELESCOPICALLY CARRIED BY THE TUBULAR SUPPORTING MEMBER AND ADJUSTABLY PROJECTING THEREABOVE, COMPRISING IN COMBINATION, AN ELONGATED BRACKET HAVING A PLURALITY OF SPACED APART NOTCHES ALONG ONE OF THE LONGITUDINAL EDGES THEREOF FOR SELECTIVELY RECEIVING THE BAIL OF THE SCREEN, AND A PAIR OF SPACED APART EARS EXTENDING FROM ONE END OF THE ELONGATED BRACKET AND PROVIDED WITH OPPOSITELY DIRECTED ALIGNED FLANGES FOR ENCOMPASSING THE EXTENSION ROD AT SPACED APART POINTS THEREALONG TO REMOVABLY MOUNT THE ELONGATED BRACKET AT 